Fused fiber optic coupler arrangement and method for use thereof

ABSTRACT

Exemplary embodiments of an article of manufacture and method according to the present disclosure are provided. For example, a first multi-clad fiber arrangement can be provided that comprises a first core and at least one first cladding which is structured to propagate at least one first electro-magnetic radiation therethrough. A second multi-clad fiber arrangement can also be provided that comprises a second core and at least one second cladding which is structured to propagate at least one second electro-magnetic radiation therethrough. Further, at least one portion can be provided in which the first and second claddings are fused to one another.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application relates to and claims the benefit of priority from U.S.Patent Application Ser. No. 61/074,339, filed on Jun. 20, 2008, theentire disclosure of which is incorporated herein by reference.

FIELD OF THE DISCLOSURE

The present disclosure relates to exemplary embodiments of a fiberoptical article of manufacture, and more particularly to fused (e.g.,mode-selective) fiber optic coupler arrangements and methods for usethereof.

BACKGROUND INFORMATION

As shown in FIG. 1, a conventional dual cladding fiber (DCF) has aninternal structure typically consisting of a core 100, an inner cladding102, an outer cladding 104, and a protection jacket 106. Both the core100 and inner cladding 102 are structured to guide an optical wave alonga longitudinal axis 108. A wave guiding mechanism is provided either bytotal internal reflection through an appropriate refractive-indexprofile (see FIG. 1) or Bragg band gap properties. The core 100 cantypically be designed to guide only a single spatial mode, so calledHE11 mode. The inner cladding 102 can guide hundreds to millions ofmultiple spatial modes. The DCF have been developed originally foroptical fiber amplifiers and lasers. Signal light propagating in arare-earth-ion-doped core of the DCF can be amplified while interactingwith pump waves guided in the cladding. Recently, it was demonstratedthat DCF can be applied in biomedical imaging. In particular, the probelight is delivered through the single-mode core to a biological sample,whereas the signal light transmitted through or reflected from thesample can be collected by the inner cladding as well as the core ofDCF. This exemplary arrangement can be advantageous over moreconventional method based on a single-mode fiber or multi-mode fiber interms of spatial resolution, light collection efficiency, etc.

In such applications using the DCF, an arrangement or a technique tolaunch or extract light in and out of either only the core or the innercladding of the DCF can be used. Conventional arrangements generallyinclude free-space optics. As shown in FIG. 2, the core mode in a DCF110 is transmitted to the core 100 of a first receiving fiber 112through lenses 113, a beam splitter 114, and a pinhole 115. The claddingmodes of the DCF 110 are received by a second fiber 117 through a beamblocker 118. However, this conventional arrangement may suffer fromsignificant insertion loss due to beam splitting and mode profilemismatch.

Accordingly, there may be a need to address and/or overcome at leastsome of the deficiencies described herein above.

SUMMARY OF EXEMPLARY EMBODIMENTS OF THE DISCLOSURE

According to exemplary embodiments of the present disclosure, it ispossible to provide an article of manufacture and a method whichfacilitates a smaller loss and the freedom from cumbersome and costlyfree-space alignment. One of the objects of the exemplary embodiments ofthe present disclosure is solve at least some of the deficiencies of theconventional arrangements and methods, and can facilitate a fused DCFcoupler which can provide efficient mode-selective beam splitting and/orcombining.

In one exemplary embodiment, exemplary embodiments of an article ofmanufacture and method according to the present disclosure can beprovided. For example, a first multi-clad fiber arrangement can beprovided that comprises a first core and at least one first claddingwhich is structured to propagate at least one first electro-magneticradiation therethrough. A second multi-clad fiber arrangement can alsobe provided that comprises a second core and at least one secondcladding which is structured to propagate at least one secondelectro-magnetic radiation therethrough. Further, at least one portioncan be provided in which the first and second claddings are fused to oneanother.

According to one exemplary embodiment of the present disclosure, thefirst and second cores can be separated from one another within theportion(s). The separation between the first and second cores within theportion(s) can be greater than a wavelength of at least one of the firstand/or second electro-magnetic radiation. In addition, a core modecoupling ratio between the first and second cores within the portion(s)can be less than about 10%, 1%, 0.1%, etc. Further, a cladding modecoupling ratio between the first and second claddings within theportion(s) can be between about 10% and 90%. between about 40% and 60%,approximately 50%, etc.

According to another exemplary embodiment of the present disclosure, thefirst and second multi-clad fiber arrangements can be double-clad fiberarrangements. Optical properties of the first and second multi-cladfiber arrangements can be substantially identical. Further, at least onesingle mode fiber arrangement can also be provided which can be coupledto the first and/or second multi-clad fiber arrangement. The single modefiber arrangement(s) can include at least one third cladding which canbe structured to prevent a propagation of an electro-magnetic radiationtherethrough.

According to still another exemplary embodiment of the presentinvention, system and method can be provided. For example, at least onefirst electro-magnetic radiation can be provided using a firstarrangement. Further, the first electro-magnetic radiation(s) can bereceived from the first arrangement and outputted to a sample using atleast one of at least two multi-clad fiber arrangements of a secondarrangement. Each of the multi-clad fiber arrangements can comprise acore and at least one cladding which can be structured to propagate thefirst electro-magnetic radiation(s) therethrough. The second arrangementfurther can comprise at least one portion in which at least one of thecladdings of at least two of the multi-clad fiber arrangements are fusedto one another.

Further, it is possible to, with at least first one of the multi-cladfiber arrangements, receive at least one second electro-magneticradiation from the sample which can be associated with the firstelectro-magnetic radiation(s), and propagate the second electro-magneticradiation(s) via the core and the cladding thereof. In addition, it ispossible to modify and/or splitting the second electro-magneticradiation(s) traveling along the cladding of the first one of themulti-clad fiber arrangements in the at least one portion to propagateat least one third electro-magnetic radiation along the cladding of atleast second one of the multi-clad fiber arrangements. Additionally, athird arrangement can be provided which is configured to detect the atleast one third electro-magnetic radiation. The second electro-magneticradiation can be a fluorescence radiation or a scattered light.

These and other objects, features and advantages of the exemplaryembodiment of the present disclosure will become apparent upon readingthe following detailed description of the exemplary embodiments of thepresent disclosure, when taken in conjunction with the appended claims.

BRIEF DESCRIPTION OF THE DRAWING(S)

Further objects, features and advantages of the present invention willbecome apparent from the following detailed description taken inconjunction with the accompanying figures showing illustrativeembodiments of the present invention, in which:

FIG. 1 is a perspective cross-sectional view of a structure of aconventional double clad fiber which includes a refractive index profilethereof.

FIG. 2 is a diagram of a conventional system which can implement freespace coupling configurations;

FIG. 3 is a side view of an exemplary embodiment of a fabrication of afused-type DCF coupler according to the present disclosure;

FIGS. 4A-4C are side views the exemplary DCF coupler implementingexemplary operating principles according to the present disclosure;

FIGS. 5A and 5B are side views further exemplary embodiments of thefused-type DCF coupler according to the present disclosure, and of anexemplary fabrication and/or implementation thereof;

FIG. 6 is a diagram of one exemplary embodiment of an imaging systemutilized an exemplary embodiment of the DCF coupler in accordance withthe present disclosure; and

FIG. 7 is a diagram of another exemplary embodiment of the imagingsystem utilized a further exemplary embodiment of the DCF coupler inaccordance with the present disclosure.

Throughout the figures, the same reference numerals and characters,unless otherwise stated, are used to denote like features, elements,components or portions of the illustrated embodiments. Moreover, whilethe subject disclosure will now be described in detail with reference tothe figures, it is done so in connection with the illustrativeembodiments. It is intended that changes and modifications can be madeto the described exemplary embodiments without departing from the truescope and spirit of the subject disclosure as defined by the appendedclaims.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

An exemplary embodiment of a method of fabricating a DCF coupler can besimilar to a conventional method for fabricating fused single-mode fibercouplers or multimode fiber couplers. In this exemplary method,intermediate jacket-stripped sections of two identical fibers contactone another and are twisted together, which can be taperedlongitudinally by applying heat. The details of this exemplary fiberfusion method are known in the art. The exemplary embodiment of the DCFfiber according to the present disclosure, at least a portion of whichis shown as a side view in FIG. 3.

For example, as shown in FIG. 3, two DCF fibers 110 and 112, which canhave identical and/or similar designs, can be tapered and fused in amiddle portion 120 by a heat source 130. The heat source 130 caninclude, but not limited to, hydrogen-oxygen flame, graphitemini-furnace, and CO2 laser. For example, during a pulling process, aprobe beam can be used to measure a coupling ratio in situ to generatecontrol feedback to optimize optical characteristics of a fabricateddevice.

FIGS. 4A-4C illustrate side views of the exemplary embodiment of thearrangement according to the present disclosure shown in FIG. 4performing exemplary operating principle according to the presentdisclosure. For example, a signal light 200 (e.g., or anyelectro-magnetic radiation) propagated in the core 100 of a first fiber110 can experience small or minimal, e.g., preferably less than 10%,coupling to the other fiber 112 after propagating through a couplerwaist section/portion 120. As a result, the signal light (e.g., whichcan be any electro-magnetic radiation) can remain as the core mode 202of the first fiber. On another hand, light or other electro-magneticradiation guided in the inner cladding, or the cladding modes 210, mayexperience strong coupling, and the output can be provided into the twoor more fibers 110, 112, e.g., with nearly equal intensity. Thisexemplary property can be achieved by controlling a degree of fusion ofthe coupler waist section/portion 120.

As the degree of fusion of the coupler waist section/portion 120 isincreased, mode coupling between cladding modes of the fibers 110, 112can start, increase gradually, and can reach to a strong couplingregime, before mode coupling between the core modes is even started. Forexample, the coupling between the core modes may typically begin whenthe V-value of the core mode is reduced to less than 1 by tapering. Forthe claddings modes, the exemplary arrangement can act as a conventionalmultimode fiber coupler. The splitting ratio of an individual claddingmode can vary from about 0 to 100%, depending on the spatial order,wavelength, and polarization, likely yielding an overall power splittingratio close to about 50/50 between the two outputs 212, 214. For minimuminsertion loss, appropriate fiber types can preferably be selected.

FIGS. 5A and 5B illustrate side views of further exemplary embodimentsof the arrangements according to the present disclosure and exemplaryperformance of exemplary procedures using such arrangements, along witha fabrication and/or an implementation of the exemplary fused-type DCFcoupler(s). In one exemplary embodiment, e.g., as shown in FIG. 5A, oneport of the above-referenced exemplary DCF coupler can be connected to asingle mode fiber 300 at an input side 310 thereof, e.g., by fusionsplicing. According to another exemplary embodiment as shown in FIG. 5B,one port of the above-referenced exemplary DCF coupler can be connectedto another single mode fiber 305 at an output side thereof, e.g., alsoby fusion splicing.

The single mode fiber(s) 300, 305 can act as a spatial mode filter canfacilitate only the core mode (i.e., light and/or electro-magneticradiation only being transmitted through the core 100) to be launched tothe coupler (shown in FIG. 5A) and to be received from the coupler(shown in FIG. 5B). Thus, such exemplary single-mode fibers 300, 305 canprevent or reduce the transmission of the light and/or any otherelectro-magnetic radiation through cladding thereof. As illustrated inFIG. 5B, e.g., the cladding modes propagating in the first fiber 110,after the coupler waist section/portion 120 can be wasted by radiationto the air or absorption in the jacket of the single mode fiber. Indeed,the light/radiation propagating along the core 100 will continue topropagate along a core 320 of the single-mode fiber 305 as well. Thecladding modes coupled to the second fiber 112 can continue to be guidedin the inner cladding.

FIG. 6 shows a diagram of one exemplary embodiment of an optical imagingsystem based on the above-described exemplary DCF coupler in accordancewith the present disclosure. For example, the single-mode fiber 300 canbe connected to a light source or another electro-magnetic radiationsource 400. The light source 400 can include, but not limited to, amonochromatic laser, a mode-locked laser, a Super-Luminescent Diode(SLD), an LED and/or a tunable source. An output of the light source 400can be delivered to an optical probe 410 through the core 100 of thefiber 110 of the exemplary DCF. The probe light/radiation can illuminatea sample 420, which can be a biological sample. The light/radiationreemitted from the sample 420 via reflection, scattering, and/orfluorescence can be received by the optical probe 410. The optical probe410 can comprises at least one or more of lens, such as, e.g., objectivelens or GRIN lens. The optical energy coupled to the core 100 of the DCFcan then be transmitted back toward the light source 400. Approximatelya half of the optical energy initially coupled in the claddings 102, 104of the first fiber 110 of the exemplary the DCF and returning from thesample 420 can be coupled to the second fiber 112 in the cladding 111,116 thereof, and can be detected by a photo-receiver 430. Thephoto-receiver 430 can include, but not limited to, a photodiode, a CCDarray and/or a CMOS array.

For example, the exemplary optical system shown in FIG. 6 can berealized for two-photon fluorescence imaging as described in M. T.Myaing et al., “Enhanced two-photon biosensing with double-clad photoniccrystal fibers,” Opt. Lett. 28, 1224-1226 (2003). In such exemplaryembodiment, the light source 400 can be a pulsed laser emitting infraredlight. The optical probe 410 can utilize a high NA objective lensfocusing the core mode to the sample 420. The fluorescent lightgenerated within the sample 420 and received by the cladding 116 of theDCF through the objective lens can then be measured at thephoto-receiver 430 through a dielectric filter filtering the pump waveand transmitting, e.g., only the fluorescence signal light. The opticalprobe 410 can include a beam scanning actuator to scan the probe beamtransversely across the sample 420.

The exemplary embodiment of the imaging system shown in FIG. 6 can alsobe configured for spectrally-encoded endoscopy as described in D. Yelinet al., “Double clad fiber for endoscopy,” Opt. Lett. 29, 2408-2410(2004). In this exemplary case, the light source 400 can include abroadband SLD, and the probe 410 can utilize a diffraction grating andlens to focus different wavelengths to different spatial points in thesample 420. The reflected light captured in the cladding 111, 116 of theDCF can be detected by, e.g., a CCD array.

The exemplary imaging system architecture of another exemplaryembodiment of the present disclosure can be extended for aninterferometric imaging by adding a single-mode fiber coupler 500, areference mirror 520, and a photodetector 540, as illustrated in FIG. 7.For an exemplary time-heterodyne detection, the reference mirror 520 canbe scanned axially. Alternatively or in addition, the photodetector 540can include a spectrometer which can have a diffraction grating and adetector array for spectral-domain detection. Further or alternatively,a wavelength-tunable light source can be used as a light source 430 foroptical frequency domain imaging. Various exemplary techniques forinterferometer-based optical imaging are known in the art.

Other exemplary embodiments of the imaging system with configurationsmodified from FIG. 6 can include reflectance confocal imaging,fluorescence detection, fluorescence confocal imaging, multi photonfluorescence microscopy, coherent Raman microscopy, and second- orthird-harmonic generation microscopy. The exemplary DCF coupler can alsobe used in cladding-pumped optical amplifiers and lasers for combiningor splitting the signal and pump waves.

The foregoing merely illustrates the principles of the invention.Various modifications and alterations to the described embodiments willbe apparent to those skilled in the art in view of the teachings herein.Indeed, the arrangements, systems and methods according to the exemplaryembodiments of the present invention can be used with imaging systems,and for example with those described in International Patent PublicationWO 2005/047813 published May 26, 2005, U.S. Patent Publication No.2006/0093276, published May 4, 2006, and U.S. Patent Publication No.2005/0018201, published Jan. 27, 2005, the disclosures of which areincorporated by reference herein in their entireties. It will thus beappreciated that those skilled in the art will be able to devisenumerous systems, arrangements and methods which, although notexplicitly shown or described herein, embody the principles of theinvention and are thus within the spirit and scope of the presentinvention. In addition, to the extent that the prior art knowledge hasnot been explicitly incorporated by reference herein above, it isexplicitly being incorporated herein in its entirety. All publicationsreferenced herein above are incorporated herein by reference in theirentireties.

1-28. (canceled)
 29. An article of manufacture, comprising: a firstmulti-clad fiber arrangement which comprises a first core and at leastone first cladding which is structured to propagate at least one firstelectro-magnetic radiation therethrough; a second multi-clad fiberarrangement which comprises a second core and at least one secondcladding which is structured to propagate at least one secondelectro-magnetic radiation therethrough; and at least one portion inwhich the first and second claddings are fused to one another.
 30. Thearticle of manufacture according to claim 29, wherein the first andsecond cores are separated from one another within the at least oneportion.
 31. The article of manufacture according to claim 30, wherein aseparation between the first and second cores within the at least oneportion is greater than a wavelength of at least one of the at least onefirst electro-magnetic radiation or the at least one secondelectro-magnetic radiation.
 32. The article of manufacture according toclaim 30, wherein a core mode coupling ratio between the first andsecond cores within the at least one portion is less than about 10%. 33.The article of manufacture according to claim 30, wherein a core modecoupling ratio between the first and second cores within the at leastone portion is less than about 1%.
 34. The article of manufactureaccording to claim 30, wherein a core mode coupling ratio between thefirst and second cores within the at least one portion is less thanabout 0.1%.
 35. The article of manufacture according to claim 29,wherein a cladding mode coupling ratio between the first and secondcladdings within the at least one portion is between about 10% and 90%.36. The article of manufacture according to claim 29, wherein a claddingmode coupling ratio between the first and second claddings within the atleast one portion is between about 40% and 60%.
 37. The article ofmanufacture according to claim 29, wherein a cladding mode couplingratio between the first and second claddings within the at least oneportion is approximately 50%.
 38. The article of manufacture accordingto claim 29, wherein the first and second multi-clad fiber arrangementsare double-clad fiber arrangements.
 39. The article of manufactureaccording to claim 29, wherein optical properties of the first andsecond multi-clad fiber arrangements are substantially identical. 40.The article of manufacture according to claim 29, further comprising atleast one single mode fiber arrangement which is coupled to at least oneof the at least one first multi-clad fiber arrangement and the least onesecond multi-clad fiber arrangement, wherein the at least one singlemode fiber arrangement includes at least one third cladding which isstructured to prevent a propagation of an electro-magnetic radiationtherethrough.
 41. The article of manufacture according to claim 29,wherein, after transmitting the at least one first electro-magneticradiation, the first multi-clad fiber arrangement receives at least onethird electro-magnetic radiation from a sample which is associated withthe at least one first electro-magnetic radiation, and propagates the atleast one third electro-magnetic radiation via the core and the at leastone first cladding thereof, and wherein the at least one thirdelectro-magnetic radiation traveling along the at least one firstcladding of the first multi-clad fiber arrangement is at least one ofmodified or split in the at least one portion to propagate at least onefourth electro-magnetic radiation along the at least one second claddingof the second multi-clad fiber arrangement.
 42. The article ofmanufacture according to claim 41, further comprising a thirdarrangement which is configured to detect the at least one fourthelectro-magnetic radiation.
 43. The article of manufacture according toclaim 41, wherein the at least one third electro-magnetic radiation is afluorescence radiation or a scattered light.
 44. A system, comprising: afirst arrangement which is configured to provide at least one firstelectro-magnetic radiation; and a second arrangement which includes atleast two multi-clad fiber arrangements at least one of which receivesthe at least one first electro-magnetic radiation from the firstarrangement and outputs the least one first electro-magnetic radiationto a sample, each of the multi-clad fiber arrangements comprising a coreand at least one cladding which is structured to propagate the at leastone first electro-magnetic radiation therethrough, the secondarrangement further comprising at least one portion in which at leastone of the claddings of at least two of the multi-clad fiberarrangements are fused to one another, wherein at least first one of themulti-clad fiber arrangements receives at least one secondelectro-magnetic radiation from the sample which is associated with theat least one first electro-magnetic radiation, and propagates the atleast one second electro-magnetic radiation via the core and thecladding thereof, and wherein the at least one second electro-magneticradiation traveling along the cladding of the at least first one of themulti-clad fiber arrangements is at least one of modified or split inthe at least one portion to propagate at least one thirdelectro-magnetic radiation along the cladding of at least second one ofthe multi-clad fiber arrangements.
 45. The system according to claim 44,further comprising a third arrangement which is configured to detect theat least one third electro-magnetic radiation.
 46. The system accordingto claim 44, the at least one second electro-magnetic radiation is afluorescence radiation or a scattered light.
 47. The system according toclaim 44, wherein the cores of the multi-clad fiber arrangements areseparated from one another within the at least one portion.
 48. Thesystem according to claim 47, wherein the cores of the multi-clad fiberarrangements within the at least one portion is greater than awavelength of at least one of the at least one first electro-magneticradiation or the at least one second electro-magnetic radiation.
 49. Thesystem according to claim 47, wherein a core mode coupling ratio betweenthe cores of the multi-clad fiber arrangements within the at least oneportion is less than about 10%.
 50. The system according to claim 47,wherein a core mode coupling ratio between the cores of the multi-cladfiber arrangements within the at least one portion is less than about1%.
 51. The system according to claim 47, wherein a core mode couplingratio between the cores of the multi-clad fiber arrangements within theat least one portion is less than about 0.1%.
 52. The system accordingto claim 47, wherein a cladding mode coupling ratio between thecladdings of the multi-clad fiber arrangements within the at least oneportion is between about 10% and 90%.
 53. The system according to claim47, wherein a cladding mode coupling ratio between the claddings of themulti-clad fiber arrangements within the at least one portion is betweenabout 40% and 60%.
 54. The system according to claim 47, wherein acladding mode coupling ratio between the claddings of the multi-cladfiber arrangements within the at least one portion is approximately 50%.55. The system according to claim 44, wherein the multi-clad fiberarrangements are double-clad fiber arrangements.
 56. The systemaccording to claim 44, wherein optical properties of the multi-cladfiber arrangements are substantially identical.
 57. The system accordingto claim 44, further comprising at least one single mode fiberarrangement which is coupled to at least one of the multi-clad fiberarrangements, wherein the at least one single mode fiber arrangementincludes at least one further cladding which is structured to prevent apropagation of at least one of the at least one first electro-magneticradiation or the at least one second electro-magnetic radiationtherethrough.
 58. A method, comprising: providing at least one firstelectro-magnetic radiation using a first arrangement; receiving the atleast one first electro-magnetic radiation from the first arrangementand outputting the least one first electro-magnetic radiation to asample using at least one of at least two multi-clad fiber arrangementsof a second arrangement, each of the multi-clad fiber arrangementscomprising a core and at least one cladding which is structured topropagate the at least one first electro-magnetic radiationtherethrough, the second arrangement further comprising at least oneportion in which at least one of the claddings of at least two of themulti-clad fiber arrangements are fused to one another; using at leastfirst one of the multi-clad fiber arrangements, receiving at least onesecond electro-magnetic radiation from the sample which is associatedwith the at least one first electro-magnetic radiation, and propagatingthe at least one second electro-magnetic radiation via the core and thecladding thereof; and at least one of modifying or splitting the atleast one second electro-magnetic radiation traveling along the claddingof the at least first one of the multi-clad fiber arrangements in the atleast one portion to propagate at least one third electro-magneticradiation along the cladding of at least second one of the multi-cladfiber arrangements.